Morphology of Pneumonia - Cases

Question 1

A 35-year-old man presents with fever (chills (cough (and rust-colored sputum))) His chest X-ray reveals lobar consolidation. Gram stain of the sputum shows lancet-shaped (gram-positive diplococci) What is the most likely diagnosis (and how would you confirm it)? What is the pathogenesis of this condition?

Answer 1

Pneumococcal pneumonia; confirmed via sputum culture or blood culture; pathogenesis involves the invasion of the respiratory epithelium by Streptococcus pneumoniae leading to inflammation.

Question 2

A 68-year-old woman with a history of COPD is admitted with fever (cough (and shortness of breath)) What are the three most common bacterial causes of acute exacerbation of COPD (and what are their distinguishing features)?

Answer 2

Haemophilus influenzae (Streptococcus pneumoniae (and Moraxella catarrhalis)); features include purulent sputum (increased dyspnea (and history of smoking)).

Question 3

An intravenous drug user presents with fever (cough (and chest pain)) He has a history of endocarditis What type of pneumonia is he most susceptible to? What are the potential complications of this type of pneumonia?

Answer 3

Aspiration pneumonia; complications include abscess formation (necrotizing pneumonia (and pleural effusion)).

Question 4

A 40-year-old man develops pneumonia after a recent trip to a hotel with a water-cooling tower He complains of high fever (cough (and muscle aches)) What is the likely causative organism (and how would you diagnose it)? What are the risk factors for this type of pneumonia?

Answer 4

Legionella pneumophila; diagnosed via urine antigen test; risk factors include travel to endemic areas (exposure to contaminated water systems).

Question 5

A 20-year-old college student presents with fever (headache (and a dry cough)) Chest X-ray reveals patchy interstitial infiltrates What are the likely causes of atypical pneumonia (and how do they differ from typical bacterial pneumonia)?

Answer 5

Mycoplasma pneumoniae (Chlamydia pneumoniae (and Legionella pneumophila)); atypical pneumonia presents with a dry cough (low-grade fever (and patchy infiltrates on X-ray)).

Question 6

A 70-year-old man with a history of heart disease is hospitalized with severe pneumonia following a flu-like illness What is the role of antigenic drift and antigenic shift in the emergence of new influenza strains?

Answer 6

Antigenic drift leads to small genetic mutations (while antigenic shift results in major changes); both allow the virus to evade immune detection (and contribute to outbreaks).

Question 7

A young child develops bronchiolitis after a viral infection Explain the morphologic changes seen in viral pneumonia (and how it can lead to complications like obliterative bronchiolitis)

Answer 7

Viral pneumonia causes inflammation (alveolar damage (and edema)); can lead to airway obstruction and fibrosis (particularly in small airways).

Question 8

Discuss the pathogenesis of influenza virus infection (focusing on the roles of hemagglutinin and neuraminidase proteins)

Answer 8

Hemagglutinin facilitates viral entry by binding to host cell receptors (while neuraminidase aids in the release of new viral particles (enabling spread and infection)).

Question 9

What are the potential long-term sequelae of viral pneumonia?

Answer 9

Long-term sequelae may include chronic cough (lung fibrosis (and impaired lung function)), particularly in those with preexisting conditions.

Question 10

A patient on mechanical ventilation develops a new fever and purulent sputum What are the most common organisms associated with hospital-acquired pneumonia (and why is this condition a serious concern)?

Answer 10

Pseudomonas aeruginosa (Staphylococcus aureus (and Klebsiella pneumoniae)); this condition is serious due to the difficulty of treating resistant organisms (and the risk of sepsis).

Question 11

A 75-year-old man with a history of stroke develops pneumonia after aspirating gastric contents Describe the pathophysiology of aspiration pneumonia and its potential complications

Answer 11

Aspiration pneumonia occurs when gastric contents are inhaled (leading to infection by anaerobic bacteria); complications include lung abscess and sepsis.

Question 12

Explain the role of microaspiration in lung pathology

Answer 12

Microaspiration can lead to chronic inflammation and infection (contributing to conditions such as aspiration pneumonia and fibrosis).

Question 13

A 50-year-old man with poor dental hygiene presents with fever (cough (and foul-smelling sputum)) Imaging reveals a cavitary lesion in his right lung What is the most likely diagnosis (and what are the common causative organisms)?

Answer 13

Lung abscess; common causative organisms include anaerobes such as Bacteroides and Fusobacterium.

Question 14

Describe the various mechanisms by which bacteria can be introduced into the lungs (leading to lung abscess formation)

Answer 14

Bacteria can enter through aspiration (hematogenous spread (or direct extension from nearby infected structures)).

Question 15

A lung abscess is discovered in a 60-year-old smoker Why is it essential to rule out underlying carcinoma in this case?

Answer 15

Lung abscess in a smoker could be mistaken for cancer (and it is important to rule out malignancy to guide treatment).

Question 16

A 45-year-old man from the Mississippi River valley presents with cough (fever (and weight loss)) A chest X-ray shows calcified nodules in his lungs What is the most likely diagnosis (and how is it acquired)? What are the clinical and morphological features of this condition?

Answer 16

Histoplasmosis; acquired via inhalation of fungal spores from soil contaminated by bat or bird droppings Clinical features include fever (cough (and granulomas on X-ray)).

Question 17

Compare and contrast the clinical and morphological features of histoplasmosis (blastomycosis (and coccidioidomycosis))

Answer 17

Histoplasmosis presents with granulomas (blastomycosis with broad-based budding yeast (and coccidioidomycosis with spherules filled with endospores)).

Question 18

A patient presents with suppurative granulomas in his lung biopsy Which fungal infection is most likely associated with this finding?

Answer 18

Blastomycosis, which often presents with suppurative granulomas.

Question 19

A patient with HIV and a CD4+ count of 150 cells/mm3 presents with fever (and shortness of breath) What are the most likely pulmonary infections in this patient?

Answer 19

Pneumocystis jirovecii pneumonia (Mycobacterium tuberculosis (and fungal infections like Histoplasmosis)).

Question 20

Discuss the general principles of HIV-associated pulmonary disease (including the role of CD4+ count in determining infection risk)

Answer 20

Low CD4+ counts (<200 cells/mm3) increase the risk for opportunistic infections (such as Pneumocystis jirovecii pneumonia and tuberculosis).

Question 21

An immunosuppressed patient develops a pulmonary infiltrate after receiving chemotherapy What are the potential infectious and noninfectious causes of this finding?

Answer 21

Infectious causes include bacterial and fungal infections (while noninfectious causes include drug-induced lung toxicity and radiation-induced changes).

Question 22

Why is the diagnostic workup of pneumonia in immunocompromised patients often more extensive?

Answer 22

Immunocompromised patients are at higher risk for unusual infections (and atypical presentations), necessitating a broader diagnostic approach.